Yes. The reason why the BGM of "Desolation" uses a flute in the key of D is that the timbre and pitch of the flute in the key of D are suitable for expressing the melody and emotion of this piece of music. The D-key flute is usually considered to be a alto-type flute with a full and mellow tone, suitable for playing some beautiful melodies and deep emotions. In the BGM of "Desolation", the D-key flute can well show the melody and emotion of the music, bringing a profound musical experience to the audience.